Question: A polynomial of degree four with leading coefficient 1 and integer coefficients has two real zeros, both of which are integers. Which of the following can also be a zero of the polynomial?

(A) $\frac{1 + i \sqrt{11}}{2}$

(B) $\frac{1 + i}{2}$

(C) $\frac{1}{2} + i$

(D) $1 + \frac{i}{2}$

(E) $\frac{1 + i \sqrt{13}}{2}$
Answer: If $r$ and $s$ are the integer zeros, the polynomial can be written in the form $$P(x)=(x-r)(x-s)(x^2+\alpha x + \beta).$$The coefficient of $x^3$, $\alpha-(r+s)$, is an integer, so $\alpha$ is an integer. The coefficient of $x^2$, $\beta - \alpha(r+s)+rs$, is an integer, so $\beta$ is also an integer. Applying the quadratic formula gives the remaining zeros as $$\frac{1}{2}(-\alpha \pm \sqrt{\alpha^2-4\beta}) = -\frac{\alpha}{2} \pm i\frac{\sqrt{4\beta-\alpha^2}}{2}.$$Answer choices (A), (B), (C), and (E) require that $\alpha=-1$, which implies that the imaginary parts of the remaining zeros have the form $\pm\sqrt{4\beta-1}/2$. This is true only for choice $\boxed{\text{(A)}}$.
Note that choice (D) is not possible since this choice requires $\alpha = -2$, which produces an imaginary part of the form $\sqrt{\beta-1}$, which cannot be $\frac{1}{2}$.